The present invention relates to a protection module, in particular for an EUV lithography apparatus, comprising a housing having at least one opening, in which at least one component is arranged and at which one or more gas feeds are provided in order to introduce a gas flow into the housing, which emerges through the at least one opening. Furthermore, the present invention relates to an EUV lithography apparatus, a projection system, an illumination system and a beam-shaping system for EUV lithography apparatuses in which at least one protection module of this type is arranged.
In EUV lithography apparatuses, reflective optical elements for the extreme ultraviolet (EUV) or soft X-ray wavelength range (e.g. wavelengths of between approximately 5 nm and 20 nm) such as photomasks, or multilayer mirrors, for instance, are used for the lithography of semiconductor devices. Since EUV lithography apparatuses generally comprise a plurality of reflective optical elements, they should have a highest possible reflectivity in order to ensure a sufficiently high total reflectivity. The reflectivity and the lifetime of the reflective optical elements can be reduced by contamination of the optically utilized reflective surface of the reflective optical elements, which arises on account of the short-wave irradiation together with residual gases in the operating atmosphere.
Since a plurality of reflective optical elements are usually arranged one behind another in an EUV lithography apparatus, even relatively small contaminations on each individual reflective optical element affect the total reflectivity to a relatively large extent.
Reflective optical elements for the EUV or soft wavelength range generally have multilayer systems. These multilayer systems have alternately applied layers of a material having a higher real part of the refractive index at the operating wavelength (also called spacers) and of a material having a lower real part of the refractive index at the operating wavelength (also called absorbers), wherein an absorber-spacer pair forms a stack. In certain respects a crystal is thereby simulated whose network planes correspond to the absorber layers at which Bragg reflection takes place. The thicknesses of the individual layers and also of the repeating stacks can be constant over the entire multilayer system or alternatively vary, depending on what reflection profile is intended to be achieved.
Contamination-sensitive components can be incorporated into protective housings. In many cases, however, it is not possible to prevent an opening from nevertheless remaining in order to ensure the functionality of the respective component. Use is therefore made of protection modules comprising a housing having at least one opening, in which at least one component is arranged, wherein one or more gas feeds are provided in order to introduce a gas flow into the housing, which emerges through the at least one opening.